As wellknown an ion implantation is utilized to perform an impurity doping or a material synthesization on a substrate by irradiating accelerated ions onto the surface thereof. The doping can be performed without any influence of the surface condition of the substrate and with very high accuracy and cleanliness. Therefore, the ion implantation may be utilized for manufacturing LSI elements, VLSI elements or the like, or synthesizing an alloy or an amorphous material.
An example of a conventional ion implantation apparatus is shown in FIG. 1 of the accompanying drawings. The apparatus shown in FIG. 1 comprises an ion source A for generating an ion beam, a mass separator B, an accelerator C, a converging lens system D, a parallel flat plate type electrostatic deflector E for deflecting the ion beam in Y direction (vertical direction), a parallel flat plate type electrostatic deflector F for deflecting the ion beam in X direction (horizontal direction), and a processing chamber which contains a substrate G to be ion implanted.
The ion beam generated by the ion source A is passed through the mass separator B by which ions having a predetermined kinetic energy and mass are selected from other ions produced in the ion source A. The ion beam containing ions selected by the mass separator B is accelerated by the accelerator C and then is converged by the converging lens system D.
In the parallel flat plate type electrostatic deflector E, the converged ion beam is swept in the Y direction by applying the voltage of a triangular wave form of for example 176 Hz, thereto. In the parallel flat plate type electrostatic deflector F, the ion beam is deflected by applying voltage for offsetting of approximately 7.degree. in the X direction and simultaneously is swept in the X direction by applying voltage of a triangular waveform having, for example, 833 Hz.
With the conventional ion implanting apparatus, as mentioned above, after being swept in Y direction by means of the parallel flat plate type electrostatic deflector E, the ion beam is subjected to the offset-deflection in X direction and the sweeping-deflection in X direction simultaneously in the parallel flat plate type electrostatic deflector F. However, since the ion beam is raster-scanned in X and Y directions and thus the ion beam appearing on the output of the deflector F does not have a constant direction, and thus the ion beam is incident on the substrate G with different incidence angles from point to point.
If the diameter of the substrate is for example 6 inches, the difference of 2.7.degree. in an implantation angle of incidence may occur between the ion beam incident on the periphery portion of the substrate and the ion beam incident on the center portion thereof. Also, with the substrate having a diameter of 8 inches, the difference in angle of incidence between the ion beam incident on the periphery portion and the ion beam incident on the center portion becomes 3.6.degree.. Between the opposite edge portions of the 6-inch substrate there may occur the difference in angle of incidence 2.7.degree..times.2=5.4.degree.. The 8-inch substrate 3.6.degree..times.2=7.2.degree..
This results in the ion implantation condition to be performed on the substrate or being different from point to point on the substrate or wafer. This phenomenon causes a shadowing effect in the ion implantation in fabricating IC elements trench constructions. Further, the uniformity of the ion implantation is deteriorated at the periphery portion of the substrate where the solid angle of the ion beam cut by the unit area of the substrate diminishes, also feasibly causing channeling at the periphery portion.
On the other hand, as the microfabrication of the substrate progresses and the pattern line width decreases, the shadowing effect in ion implantation has an unfavorable influence on the processing of the substrate. For a CMOS DRAM having 4M bits of memory or more, thus, it is necessary to ion implant the whole surface of the substrate with an ion beam pointed parallel to a definitely predetermined direction. More specifically, as the substrate size is increased from 6 to 8 inches and the memory size of the DRAMs increases to 4M or further 16M bits, and thus the pattern width is reduced, the need of parallel ion beam implantation has become to be closed-up.
It is, therefore, an object of the present invention is to overcome the problems involved in the conventional ion implantation apparatus.
Another object of the present invention is to provide an ion implantation apparatus which is capable of incidenting an ion beam all over a substrate at a constant incident angle without any deterioration of the characteristic thereof.
Another object of the present invention is to provide an ion implantation apparatus having a simplified deflector scanner system.
Another object of the present invention is to provide an ion implantater apparatus which is capable of providing a parallel scanning ion implantation of a substrate regardless of the size thereof.
A further object of the present invention is to eliminate any concentration of neutral particles produced from high energy ions by a charge exchange with atoms of residual gases at any local spot on the substrate which would seriously deteriorate the uniformity of the doping.